1. Field of the Invention
This invention pertains generally to power bus apparatus and, more particularly, to apparatus, such as sensors, powered from a power bus.
2. Background Information
Electrical sensors of various types are used to detect the current flowing through a conductor. Such sensors include, for example, a single Hall effect sensor that produces an output voltage indicative of the current magnitude as well as more conventional current sensors such as a shunt resistor.
Hall effect devices have been used to sense variations in magnetic flux resulting from a flow of current through a conductor. Some of these known devices have used a flux concentrator to concentrate magnetic flux emanating from the flow of current through the conductor. It has previously been suggested that electrical current sensing apparatus could be constructed in the manner disclosed in U.S. Pat. Nos. 4,587,509; and 4,616,207.
It is also known to measure the current in a conductor with one or two appropriately placed Hall sensors that measure flux density near the conductor and to convert the same to a signal proportional to current. See, for example, U.S. Pat. Nos. 6,130,599; 6,271,656; 6,642,704; and 6,731,105.
U.S. Pat. No. 7,145,322 discloses a power bus current sensor, which is powered by a self-powered inductive coupling circuit. Sensors sense current or temperature of the power bus. A microprocessor inputs the sensed current and the sensed temperature from the sensors and outputs corresponding signals to a radio transceiver circuit. A power supply employs voltage produced by magnetically coupling the power bus to one or more coils, in order to power the sensors, the radio transceiver circuit and the microprocessor from flux arising from current flowing in the power bus. Suitable power management routines are employed to help save power consumption by putting the microprocessor into a sleep (e.g., low-power) mode and waking up when data is to be sent. Peak power is supplied by capacitors in the power supply during relatively short durations of transmission or reception. Otherwise, the radio transceiver circuit is preferably turned off.
U.S. Patent Application Pub. No. 2007/0007968 discloses a system for monitoring an electrical power system including one or more transducer units, each of which has a current measuring device and a voltage measuring device coupled to a respective one of the phase conductors of the power system, and a transducer wireless communications device. The transducer unit includes a battery for providing power to the components thereof. The battery is connected to a trickle charger, which, in turn, is electrically coupled to a phase conductor. The trickle charger is a known parasitic power charger that draws power from the phase conductor and uses it to charge the battery.
There is room for improvement in sensors and other apparatus for power busses.